A thin-film-transistor liquid crystal display (hereinafter referred to as TFT LCD) includes a first substrate and a second substrate arranged opposite with and aligned to each other, and a liquid crystal layer interposed between the first substrate and the second substrate.
In an existing TFT LCD, thin-film transistors are provided on the first substrate, which are used as driving switches. Color filters and a black matrix are provided on the second substrate, the color filters being used to implement a color display, the black matrix being used to shield the thin-film transistors and signal lines. In such a TFT LCD, it is inevitable that the first substrate and the second substrate are arranged opposite with and aligned to each other with an arrangement deviation, and thus the black matrix is required to have a relatively large width, so as to be capable of shielding the thin-film transistors and signal lines with the occurrence of the arrangement deviation. However, an aperture ratio would be reduced due to the black matrix having a relatively large width, thereby affecting the brightness as well as the image quality of a display panel.
In another existing TFT LCD, the thin-film transistors, the color filters and the black matrix are provided on one substrate, i.e., a technique of color filter on Array (COA), and FIG. 1 illustrates a structure of a display panel of such a TFT LCD. Specifically, the display panel of the TFT LCD includes a first substrate 1, a second substrate 2 and a liquid crystal layer 3, wherein a spacer 4 is disposed between the first substrate 1 and the second substrate 2 to maintain a distance between the first substrate 1 and the second substrate 2, i.e., a thickness of the liquid crystal layer 3. A thin-film transistor 10, a first insulation layer 11, a black matrix 12, a color filter 13, a planarization layer 14, a pixel electrode 15, a second insulation layer 16 and a common electrode 17 are disposed on the first substrate 1, in which the thin-film transistor 10 includes a gate electrode 100, a gate insulation layer 101, an active layer 102, a source electrode 103 and a drain electrode 104. The first insulation layer 11 and the second insulation layer 16 are generally made of silicon nitride (SiNx).
In such a TFT LCD, the thin-film transistor 10, the color filter 13 and the black matrix 12 are provided on the first substrate 1, so as to avoid influencing on the shielding effect of the black matrix 12 on the thin-film transistor 10 and the signal lines due to the arrangement deviation between the first substrate and the second substrate, and thus there is no need to provide the black matrix 12 with a relatively large width. Accordingly, compared with the previous TFT LCD, the aperture ratio of the display panel may be increased by using the TFT LCD, thereby improving the brightness and the image quality of the display panel.
However, in the above TFT LCD employing the COA technique, it is difficult to form a pattern of the black matrix 12 on the first insulation 11, and such problem has emerged that, the material of the black matrix 12 in the prior art cannot meet the requirement of a high resolution for the display panel; the material of the black matrix 12 has an insufficient adhesion capability to the material of the first insulation layer 11 (e.g., SiNx or the like), resulting in an unstable structure of the display panel; and, after the development step of the lithography process for forming the pattern of the black matrix 12, a residue of the material of black matrix easily remains on a surface of the first insulation layer 11, resulting in display defects.